1. Technical Field
The present invention relates to a photoconductive antenna, a terahertz wave generating device, a camera, an imaging device, and a measuring device.
2. Related Art
In recent years, attention has been devoted to terahertz waves, which are electromagnetic waves with frequencies of 100 GHz or greater and 30 THz or less. Terahertz waves can be used in various forms of measurement and non-destructive testing such as imaging and spectrometry.
The terahertz wave generating device that generates these terahertz waves has a light source device that generates light pulses (pulsed light) having pulse widths at the approximately sub picosecond level (several hundred femtoseconds) and a photoconductive antenna that generates terahertz waves by irradiating light pulses generated by the light pulse generator.
As the photoconductive antenna, for example, disclosed in Japanese Laid-Open Patent Application Publication No. 2010-50287 is a pin structure photoconductive element (photoconductive antenna) which has an n type semiconductor layer, an i type semiconductor layer, and a p type semiconductor layer. With this photoconductive antenna, the n type semiconductor layer is provided at one surface side of the i type semiconductor layer, and the p type semiconductor layer is provided at the other surface side. Also, the n type semiconductor layer and the p type semiconductor layer are arranged to be skewed in relation to each other in the thickness direction of the i type semiconductor layer. Note that the terahertz waves are emitted in the direction perpendicular to the direction of the electric field.
With the photoconductive antenna noted in the above mentioned publication, for a dipole shaped photoconductive antenna (PCA) manufactured using a low temperature growth GaAs (LT-GaAs) substrate, it is possible to make the intensity of the generated terahertz waves approximately 10 times larger.